The process of setting up a character for animation in computer graphics is often intricate and time-consuming. For example, setup of a character skeleton and the corresponding deformation thereof have typically been approached from the inside out. This means that the setup artist typically places all of the joints within the skin, runs a script and then continues to place additional features by hand. To do this by hand means that the artist manipulates the digital entities representing these features using the input device of a computer (e.g., a mouse or track pad). Then, the artist may perform muscle setup by hand in a similar way. When the character is finished, it will be used as a tool in providing the successively changing appearance of the character in generating the animation.
With increasing complexity of animation, the work needed for character setup increases significantly, sometimes by several orders of magnitude or more. This is because complicated animation features such as sliding skin and muscle deformations require progressively greater amounts of time in setting up the character. Also, rigging of the character typically involves building a single hierarchy of nodes to represent the motion that drives the character. These rigs usually are not flexible and do not allow a convenient way of making rapid changes to the character structure, for example in response to feedback from directors or animators on the project.